1. Field of the Invention
The present invention relates to an ocular refracting power measuring system which is particularly useful for infants and even for babies.
2. Description of the Related Art
There are known ocular refracting power measuring systems which include a so-called subjective type ophthalmoscope for measuring the ocular refracting power of a patient in accordance with his response, a so-called auto-refractomer for objectively measuring the ocular refracting power and so on.
When it is to measure the ocular refracting power of babies using such types of systems, the subjective type opthalmoscope cannot measure it since cooperation from the babies cannot be obtained. The general auto-refractometer is extremely difficult to measure the ocular refracting power of babies since they cannot easily be fixed in position relative to the auto-refractometer.
In order to overcome such defects, there has been proposed a so-called photo-refraction type measuring process which consists of illuminating the eyeground of a patient by the use of a strobo flash, photographing the state of the beam at the pupil of the patient and determining the refracting power from the photographed result.
It was believed that the photo-refraction type measuring process was useful in measuring the ocular refracting power of babies since the measurement can be sufficiently performed even if the optical axis of the eye to be tested was deflected slightly out of the normal measurement axis.
In the ocular refracting power measuring system of the photo-refraction type, the beam of stroboscopic light is directed slantly to the optical axis of the camera so that only the image of the pupil wlll be photographed. However, there are values of diopter which cannot be measured by the position of the light source. The photo-refraction type system also has a problem in that it can measure the ocular refracting power only within a reduced range of measurement.